1. Field of the Invention
The present invention relates to an ink jet head for applying pressure to pressure chambers and thus ejecting ink drops from nozzles, and in particular to a multi-nozzle ink jet head for performing lead out of electrodes from a row of piezoelectric bodies using a laminate of the elements.
2. Description of the Related Art
An ink jet recording head has nozzles, ink chambers, an ink supply system, an ink tank, and transducers; by transmitting displacement/pressure generated by the transducers to the ink chambers, ink particles are ejected from the nozzles, and characters or images are recorded on a recording medium such as paper.
In a well-known form, a thin-plate-shaped piezoelectric element having the whole of one surface thereof bonded to the outer wall of an ink chamber is used as each transducer. A pulse-like voltage is applied to the piezoelectric element, thus bending the composite plate comprising the piezoelectric element and the outer wall of the ink chamber, and the displacement/pressure generated through the bending is transmitted to the inside of the ink chamber via the outer wall of the ink chamber.
A sectioned perspective view of a conventional multi-nozzle ink jet head 100 is shown in FIG. 21. As shown in FIG. 21, the head 100 is constituted from a row of piezoelectric bodies 111, individual electrodes 112 that are formed on the piezoelectric bodies, a nozzle plate 114 in which are provided nozzles 113, ink chamber walls 117 made of a metal or a resin that, along with the nozzle plate 114, form ink chambers 115 corresponding to the nozzles 113, and a diaphragm 116.
A nozzle 113 and a piezoelectric body 111 are provided for each ink chamber 115, and the periphery of each ink chamber 115 and the periphery of the corresponding part of the diaphragm 116 are connected together strongly. A piezoelectric body 111 for which a voltage has been applied to the individual electrode 112 deforms the corresponding part of the diaphragm 116 as shown by the dashed lines in the drawing. As a result, an ink drop is ejected from the nozzle 113.
Application of voltages to each of the piezoelectric bodies 111 is carried out separately using electrical signals from a printing apparatus main body via printed circuit boards. FIG. 22 is a drawing showing the constitution of connections between the conventional head and the printed circuit boards. In the example of FIG. 22, the head 100 has 8 rows and 8 columns of nozzles 113, i.e. of piezoelectric bodies 111 and individual electrodes 112. Corresponding to this, flexible printed circuit boards 110 are provided for connecting the driver circuitry of the apparatus and the individual electrodes 112 together.
In this prior art, the terminals of the printed circuit boards 110 are connected to the respective individual electrodes 112 by wires 120 through wire bonding. Moreover, art in which an FPC wiring board is connected directly is also known.
Moving on, due to demands to increase printing resolution, there are demands to increase the density of the nozzle arrangement of heads. If the nozzle density is raised, then the contact spacing between terminals (individual electrodes) is reduced. For example, the nozzle density of a head using piezoelectric bodies is currently about 150 dpi, but is advancing to 180˜300 dpi, and further to 360 dpi, and hence the contact spacing is becoming lower. However, currently the best contact spacing with wire bonding using semiconductor manufacturing is 150 dpi, with 300 dpi contacts being developed in the case of FPC connection.
Consequently, if electrical connection is carried out by providing contacts on top of or near to the piezoelectric bodies 111 as conventionally, then a problem of joining of neighboring contacts (shorting) may arise. Moreover, when connecting a large number of points in a short time, the load on the piezoelectric bodies 111 becomes very high, and with thin-film piezoelectric bodies there is a risk of breakage, and hence connection is extremely problematic.